title: Influence of adhesive restorations on diffusion of H2O2 released from a bleaching agent and its toxic effects on pulp cells.
abstract: OBJECTIVE
  To assess the influence of adhesive restorations on hydrogen peroxide (H2O2) diffusion through enamel and dentin and its cytotoxicity to pulp (MDPC-23) cells.
  
  
  METHODS
  Sound and resin-restored enamel/dentin disks were stored in water for 24 h or 6 months and adapted to artificial pulp chambers. Bleaching gels with 20% or 35% H2O2 were applied to the enamel surface for 45 min, and a culture medium in direct contact with the dentin surface (extract) was applied for 1 h to the MDPC-23 cells. Cell metabolism (MTT assay) and cell morphology (SEM) were assessed. The amount of H2O2 in the extracts was also quantified (peroxidase/leuco-crystal violet reaction).
  
  
  RESULTS
  A significant reduction in cell metabolism was observed between the group bleached with the 35% gel and the control group (sound, nonbleached) (p < 0.05). The H2O2 diffusion was directly related to its concentration in the bleaching gel. The variables "presence of restoration" and "time of water storage" did not significantly influence H2O2 diffusion or cell metabolism for either of the bleaching gels (p > 0.05). All bleached groups presented alterations in cell morphology related to the concentration of H2O2 in the bleaching gel.
  
  
  CONCLUSIONS
  The reduction in cell metabolism and the changes in cell morphology were H2O2-concentration dependent, having no relationship with the presence of either new or aged adhesive restorations on teeth subjected to bleaching therapies.
authors.forename: Diana Gabriela
authors.initials: DG
authors.lastname: Soares
authors.forename: Júlia Vieira
authors.initials: JV
authors.lastname: Pastana
authors.forename: Carla Caroline
authors.initials: CC
authors.lastname: de Oliveira  Duque
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Dias Ribeiro
authors.forename: Fernanda Gonçalves
authors.initials: FG
authors.lastname: Basso
authors.forename: Josimeri
authors.initials: J
authors.lastname: Hebling
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: de Souza Costa
mesh_terms: D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002417:Cattle; D018929:Cell Culture Techniques; D002460:Cell Line; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003188:Composite Resins / Q000737:chemistry*; D003743:Dental Enamel / Q000187:drug effects; D003764:Dental Materials / Q000737:chemistry*; D003782:Dental Pulp / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D003793:Dental Restoration, Permanent; D003804:Dentin / Q000187:drug effects; D004058:Diffusion; D015194:Diffusion Chambers, Culture; D006861:Hydrogen Peroxide / Q000633:toxicity*; D008297:Male; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D013997:Time Factors; D058205:Tooth Bleaching Agents / Q000633:toxicity*; D014867:Water / Q000737:chemistry
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D058205:Tooth Bleaching Agents; C533204:filtek Z350; C115612:single bond; D014867:Water; D017438:Bisphenol A-Glycidyl Methacrylate; D006861:Hydrogen Peroxide